1. Field of the Invention
The present invention relates to hard disk recorders. In particular, the present invention relates to a hard disk recorder having a time-shift playback function of storing a program which is now being received, displaying the stored program, even if program-storing is still under way, in such a manner that the program is displayed from an arbitrary section of the program among program sections that have already been stored, and pausing the display of the program or changing the display speed according to an operation by a user while the program is being watched.
2. Description of the Background Art
A hard disk recorder is disclosed as a TV program-watching device in Japanese Patent Laying-Open No. 2002-44542. Such a hard disk recorder was put into practical use as low-cost manufacturing of a large-capacity hard disk (hereinafter referred to as HDD) was achieved. The conventional video tape recorder (VTR) can perform only recording or playback at a time, and thus it cannot play back a recorded program until it completes recording of the program. On the other hand, the hard disk recorder has a feature that it can use the time-shift playback function to display a program, even if storing of the program on the HDD is under way, from an arbitrary section of the program among program sections that have already been stored. The hard disk recorder includes such a buffer as shown in FIG. 4 for successively storing information concerning selected programs. In the example shown in FIG. 4, the program information is stored in the order of channel 1, channel 2, external input, channel 1.
Regarding the already-proposed hard disk recorder, however, when the user switches the channel of the program which is being stored from channel 1 to channel 2, the user cannot watch already-stored contents of channel 1 any more, despite that information about the program which has been recorded is stored in the buffer. This is for the reason that a sector address of the HDD that indicates which section of the program is being played back is cleared and returned to a leading address and thus it cannot know which section of the program was lastly played back.
Therefore, when the program is being stored, switching of the channel or switching of the input source is inhibited or the time-shift playback function is stopped. Thus, the user is required to take care that the user never switches the channel or switches the input source when the time-shift playback function is effective. Moreover, the already-proposed hard disk recorder has a disadvantage that switching of the channel takes a considerable time.
FIG. 5 is a flowchart illustrating the conventional channel-switching operation. When an instruction to switch the channel is issued, a stop command is output from a control IC chip. This stop command includes a pause command in step SP (only shown as SP in the drawing) 1, an idle command in step SP2 and a stop command in step SP3. Instep SP1, if the instruction is issued, the HDD is set in a pause state from which a program-storing operation can immediately be started, without stopping such a hardware structure as HDD. In step SP2, the HDD is set in a recording-wait state, namely idle state and then set in a stop state in step SP3. In step SP4, the channel switching operation is carried out.
In step SP5, it is determined whether or not playback of stored images by the HDD is possible. This determination is done according to a status of the control IC chip. If playback is possible, the control IC chip outputs a playback command. The playback command includes a stop command in step SP6, an idle command in step SP7 and a pause command in step SP8. According to the playback command, the HDD is set in a stop state in step SP6, in an idle state again in step SP7, and a pause state in SP8. Then, in step SP9, the playback operation is carried out.
In the conventional channel-switching operation, the stop command and the playback command from the control IC chip are used to completely stop the HDD before the channel is switched and make a transition to the playback state by operating the HDD. When the HDD is stopped, the sector address of the HDD is cleared and returned to a leading address. Therefore, it cannot know which section of the program was lastly played back before the channel was switched. There is a further problem that the channel switching operation takes several tens of seconds.